Introduction: Experimental data in preschool aged children proves the determining role of the auditory and visual processes for future reading skills, therefore the investigation of complex forms of visual perception in this age period is diagnostically important.

Objectives: Basic aim of the research is assessment of the sensitive period for the non-verbal perceptive operations in pre-school aged children, and determination of subgroup with low results for non-verbal perception.

Methods: The dynamics of the visual per-ception (visual gnosis) in typically develop¬ing children were tested with an adapted version of the Poppelreuter-Ghent Test for figure-ground segregation. The total number of overlapping objects is 33, grouped accor¬ding to the level of difficulty. The children are given a group of objects separately in a following sequence and they should segregate and name the objects.

Results: A number of 365 typically developing children without diagnosis of visual disorders and without corrected visus took part in the research. All children, aged 4, 5, and 6 from three different settlements attend state nursery schools and have Bulgarian as a mother tongue. A three-factor dispersion analysis was held to define the statistical significance of the independent factors age, gender and settlement. The research’s data define the 5 year olds as sensitive about the dynamics of the complex forms of visual perception, compared to the four year old children (p<0.000009) and the six year old children (p<0.001650). The influence of the demographic factor is engaged with the significantly better results of the children from the big town compared to the capital (p<0.000926) and small town (p<0.000700). The influence of the gender as a factor is due to the better functioning of the non-verbal perceptive operations in the females (F = 1,346, p<0.019). According to the additional analysis, 25% of the children at the age of six demonstrate a low rating of the complex forms of non-verbal visual gnosis that could be reviewed as risk for developing dyslexia.

Conclusion: In the age period 4 – 6, there is a process of dynamic maturation of the right-hemispheric structures of the ventral visual system, leading to substantial improvement of the abilities for discrimination of objects in visual crowding. Poppelreuter’s test allows an objective assessment of the state of the non-verbal perceptive abilities in pre-school age and could be used in the diagnostics of predictors for dyslexia.